A Larry Clark photo taken in Oklahoma City, 1973, which features in the Another Kind of Life exhibition.
Photograph: Larry Clark/Publicity image

In 1956, Colin Wilson published The Outsider, one of that year’s most talked-about books. Using characters created by the likes of Dostoevsky, Kafka and Camus, Wilson explored the turbulent psyche of the outsider, an existential everyman driven by irrational impulses and nihilistic views. “The average man is a conformist, accepting miseries and disasters with the stoicism of a cow standing in the rain,” declared Wilson. “For the Outsider, the world is not rational, not orderly.”

That same year, as if he had arrived from another universe, Elvis Presley was causing moral panic across America during his first nationwide concert tour. Somewhere between the existential alienation that Wilson identified as a strain of literary outsiderdom and the instinctive sexuality that the young Presley exuded lies the historical and conceptual starting point for Another Kind of Life: Photography on the Margins. Spanning the 60 years since Presley shook things up with just a wiggle of his hips, it features the work of 20 photographers, including Diane Arbus, Mary Ellen Mark, Boris Mikhailov and Alec Soth. The theme is marginality, whether imposed by mainstream society or self-expressed through gender, sexuality, identity or political rebellion.

Larry Clark was 13 years old when he saw Presley perform in a Tulsa fairground in April 1956. “It was just amazing,” he recalled more than 50 years later. “It was really dirty.” With his 1960s series, Tulsa, Clark would define the notion of dirty realism in photography and his images are still about as powerful and as morally ambiguous as it gets, even in a show about often extreme outsiders. Tulsa depicts the chaotic lives of his junkie friends in the town he grew up in. He photographed them hanging out, making out and shooting up, their clandestine lifestyle happening in the heart of America in the booming postwar era. Clark’s positioning of himself as one of his subjects as well as their chronicler is what gives the series its disturbing power: there is no detachment, no humanist undertow to offer the viewer any sense of moral reassurance. His junkies are not furtive or ashamed. On the contrary, they appear cavalier and gleefully amoral – one girl grins as she squirts water from a syringe.

Clark is the quintessential outsider as insider, a stance that is adopted in different ways throughout the exhibition, not least in the tender early work of Bruce Davidson, whose 1959 Brooklyn Gang series remains one of the earliest, and most sympathetic, depictions of aberrant postwar youth culture. It finds an echo here in Philippe Chancel’s seldom seen series on young anti-fascist rockabilly gangs in 80s Paris. In both, the studied cool of the protagonists hints at the ways in which rebellion has since been presented as outlaw chic in style mags and on the catwalk.

Representations of gender and transgender people are constants, too, particularly in Chilean photographer Paz Errázuriz’s evocative portraits of male cross-dressers who worked as prostitutes throughout the terror and persecution of the Pinochet regime. A schoolteacher turned activist, Errázuriz was a self-taught photographer who for a time lived with some of her subjects in a brothel. Her attitude is in stark contrast to some of the better-known artists here, not least Diane Arbus, whose portraits of the so-called freaks that she sought out and identified with retain an unsettling power despite their familiarity. Even more so, Boris Mikhailov’s series The Wedding (2005-06), for which he paid two “bomzhes” (homeless people) to re-enact a marriage ceremony for his camera. Like Arbus, Mikhailov creates images whose impact relies on our discomfort and embarrassment as viewers of other people’s strangeness. He makes us complicit in the questionable pact between photographer and subject.

To one degree or another, all the work in the exhibition occupies that same uneasy terrain, often highlighting the various strategies photographers have employed in order to represent the “other” without objectifying or exoticising their subjects. Jim Goldberg’s democratic approach began with him befriending the young, homeless outsiders he photographed in Los Angeles and San Francisco for his hard-edged but humanist series Raised By Wolves. He filmed and photographed them as they killed time between turning tricks and scoring drugs, as well as using their handwritten testimonies and those of their parents and social workers. The result is a portrait of young survivors in an unforgiving America. One of his central characters was a kid called Tweeky Dave, who did not survive. It is his denim jacket, bequeathed to Goldberg and covered in often obscene felt-tip scrawls, that hangs from the ceiling like a relic – and an accusation.

Among the surprises at the Barbican are the more obscure series unearthed by curator Alona Pardo: Igor Palmin’s Russian hippies; Chancel’s retro rockabilly rebels; Seiji Kurata’s yakusa gangsters at play in the Tokyo clubs and gambling dens they control. A word, too, for Dayanita Singh’s deft blending of the still and moving image in her ode to Mona Ahmed, an ageing Indian eunuch whose outsiderness seems almost holy.

At the National Portrait Gallery, four pioneers of early British portrait photography are reconsidered in Victorian Giants: The Birth of Art Photography. Here, the subtext is not really art but privilege: Lewis Carroll was an Oxford academic, Julia Margaret Cameron a product of colonial Ceylon, and Lady Clementina Hawarden as aristocratic as her name suggests. (Some of the photographs have been selected by the Duchess of Cambridge, who wrote her undergraduate thesis on Victorian photography.)

Purify My Heart, also known as The Little Sisters, by Oscar Rejlander. Photograph: Oscar Rejlander/National Portrai/PA

The most intriguing figure is their mentor, Oscar Rejlander, whom the National Portrait Gallery describes as both “a Swedish émigré with a mysterious past” and the “father of Photoshop”. His composite photograph Two Ways of Life (1856-57), in which he combined several different negatives to create a single image, is the conceptual centrepiece, but this is essentially a show about the birth of a very British kind of portraiture.

Cameron’s stately photographs of contemporary writers such as Carlisle and Tennyson enshrine their literary greatness, while her more allegorical images of Mary Pinnock as Ophelia say much about Victorian ideals of female beauty. Children, too, are portrayed as vessels of innocence throughout, though Carroll’s relentless fascination with the young Alice Liddell makes for even more complex viewing in an age when children have become an almost taboo subject in photography.

The curatorial claim that Victorian portraiture was “raw, edgy and experimental” is overstating the case somewhat as only Rejlander convinces as an early avant gardist. His series of staged self-portraits in which he mimics expressions of emotion – surprise, apology, disgust and, oddly, shrugging – have a postmodern feel. The rest is familiar, perhaps overfamiliar in the case of Carroll and certainly Cameron, who has had two London gallery retrospectives in the past few years. An intriguing exploration of the formative years of a medium that had yet to find its essentially democratic voice.